Preparation of carboxylic acid esters



United States Patent ()fiice g 3,194,82 Patented any is, was

3,194,822 PREPARATKON F CARBOXYLIC ACID ESTERS David D. Neiswender, Jan, Haddonfield, and Robert D. Ofi'enhauser, Seweil, N.J., assignors t0 Socony Mobil Oil Company, Inc., a corporation of New York No Drawing. Filed Mar. 26, 1962, Ser. No. 182,658 8 Claims. (Cl. 260410.9)

' rium. If one component is readily removed from the reaction, this equilibrium can be displaced. When one of the interchange products is the component readily removed, the reaction can proceed to good yields of desired ester.

It is the discovery of this invention that methyl or ethyl esters of fatty acids can be converted into higher alkyl esters by ester interchange with the corresponding higher alkyl borates. The methyl or ethyl borate product of the equilibrium can be readily removed from the reaction, thereby effecting food conversion into the higher alkyl fatty acid ester.

Accordingly, it is a broad object of this invention to provide a method of effecting ester interchange. Another object is to provide a method for converting ethyl or methyl fatty acid esters into higher alkyl fatty acid esters. A specific object is to provide a method for effecting esterester interchange between ethyl or methyl fatty acid esters and higher alkyl borates. Other objects and advantages of this invention will become apparent to those skilled in the art, from the following detailed description.

The present invention provides a method for converting methyl or ethyl fatty acid esters into higher alkyl fatty acid esters that comprises reacting a methyl or ethyl ester of a fatty acid having between about 8 and about 30 carbon atoms and a trialkyl borate having between about 4 and about 18 carbon atoms per alkyl group, with or without an acid catalyst, at a temperature of between about 175 C. and about 300 C., under a pressure of between about 0.1 atmosphere and about one atmosphere, and continuously removing trimethyl or triethyl borate.

The fatty acid ester reactant contemplated herein is a methyl or ethyl ester of a fatty acid having between about 8 and about 30 carbon atoms per molecule and, preferably, between about 10 and about 18 carbon atoms. These methyl or ethyl esters are readily prepared by many methods well known in the art. Non-limiting examples of the fatty acid ester reactant are methyl octanoate, ethyl octanoate, methyl Z-ethylhexanoate, methyl valerate, ethyl decanoate, ethyl isodecanoate, methyl dodecanoate (methyl laurate), ethyl dodecanoate, ethyl tetradecanoate, ethyl tetradecanoate, methyl pentadecanoate, ethyl hexadecanoate, methyl octadecanoate, ethyl octadecanoate, methyl eicosanoate, ethyl docosanoate, methyl pentacosanate, ethyl octacosanate, and methyl triacontanate.

The alkyl borate reactant is a trialkyl borate having between about 4 and about 18 carbon atoms per alkyl radical. The borate esters are readily prepared by heating boron oxide (B 0 with the desired alcohol at temperatures of the order of about 100 C. and higher. Non-limiting examples of the alkyl borate reactant are tributyl bo rate, triisoamyl borate, triamyl borate, trihexyl borate, triisohexyl borate, tri-(Z-ethylhexyl) borate, trioctyl borate, trinonyl borate, tridecyl borate, tri-dodecyl borate, tritetradecyl borate, tri-hexadecyl borate, and tri-oct-a'decyl borate.

The molar ratio of the methyl (or ethyl) ester of fatty acid reactant to alkyl borate reactant will be at least 3, i.e., at least the stoichiorhetric amount. It can be advantageous to use an excess.

The temperature at which the ester interchange is effected is dependent to a large extent upon the pressure. When operating at about atmospheric pressure, temperatures between about 240 C. and about 300 C., preferably between about 25 0 C. and about 300 C., are most effective. However, operation under reduced pressures will permit the use of lower temperatures. Superatmospheric pressures do not appear to be advantageous in this process. Thus, at pressures approaching 0.1 atmosphere,

temperatures as low as about C. can be employed.

In general, therefore, the process of this invention can be carried out at temperatures between about 175 C. and about 300 C. and at pressures between about 0.1 atmosphere and about one atmosphere.

Although it is not necessary to the process, the use of an acid catalyst can be advantageous. Typical catalysts are hydrochloric acid, phosphoric acid, and sulfuric acid. Sulfuric acid is particularly preferred. The amount of catalyst used is very small, in the order of about 0.1 to 0.5 percent, by weight of the reactants.

As has been mentioned hereinbefore, the ester interchange reaction is driven toward completion by removing trimethyl or triethyl borate from the reaction zone. Thus, any apparatus can be employed that will permit the removal of the more volatile borate ester product while rctaining the remaining materials in the reaction zone. Thus, for example, there can be used a jacketed autoclave provided with a reflux column having a condenser takeoff. The time of reaction will depend upon the efliciency of removal of the volatile borate ester, and upon the temperature and pressure conditions employed. In general, the time of reaction can vary between about 0.5 hour and about 48 hours, preferably between about 2 hours and about 24 hours.

EXAMPLE 1 Reaction time, hrs

2 Yield butyl lanrate, percent l0 EXAMPLE 2 Using the same reactants and amounts thereof and the apparatus of Example 1, another run was made at a temperature of C. and under a reduced pressure of 150 mm. mercury (about 0.2 atmosphere). The progress of this run, as shown by vapor phase chromatographic analysis, is set forth in Table II.

Table II Reaction time, hrs 1 Yield butyl laurate, percent 71 EXAMPLE 3 Another run was carried out as described in Example 1, except that 2 drops of concentrated sulfuric acid were added to the reaction mixture as a catalyst. The progress Table III Reaction time, hrs Yield butyl laurate, percent r- Although the present invention has been described with preferred embodiments, it is to be understood that modifications and variations may be resorted to, without departing from the spirit and scope thereof as those skilled in the art may readily understand. Such variations and modifications are considered to be within the purview and scope of the appended claims.

What is claimed is:

1. A method for converting fatty acid esters into higher alkyl fatty acid esters that comprises reacting an ester selected from the group consisting of methyl and ethyl esters of fatty acids having between about 8 and about 30 carbon atoms and a trialkyl borate having between about 4 and about 18 carbon atoms per alkyl group, at a temperature of between about 175 C. and about 300 C., under a pressure of between about 0.1 atmosphere and about one atmosphere, and continuously removing an ester of the group consisting of trimethyl borate and triethylborate.

2. The method defined in claim it wherein said method is carried out in the presence of a mineral acid catalyst.

3. A method that comprises reacting a methyl ester of a fatty acid having between about 10 and about 18 carbon atoms and a trialkyl borate having between about 4 and about 18 carbons atoms per alkyl group, at a temperature of between about 240 C. and about 300 C., at about atmospheric pressure, and continuously removing trimethyl borate.

4. The method defined in 3 wherein said method is carried out in the presence of a mineral acid catalyst.

5. A method that comprises reacting methyl. laurate with tributyl borate, at a temperature of between about 240 C. and about 300 C., at about atmospheric pressure, and continuously removing trimethyl borate.

d. The method defined in claim 5, wherein said method is carried out in the presence of sulfuric acid.

'7. A method which comprises reacting a methyl ester of a fatty acid having between about 10 and about 18 carbon atoms and a trialkyl borate having between about 4 and about 18 carbon atoms peralkyl group, at a temperature of between about C. and about 240 C., under reduced pressure, and continuously removing trimethyl borate.

8. The method defined in claim '7 wherein said methyl ester is methyl laurate, and said trialkyl borate is tributyl borate.

Owen et al., Journal otthe Science of Food and Agriculture, 7, 88- 2 (1956).

Iublishers Inc,

CHARLES B. PARKER, Primary Examiner.

TOBIAS E. LEVOW, DANIEL D. HGRWITZ,

Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,194,822 July 13, 1965 David D. Neiswender, Jr. et a1 I It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 29, for "food" read good line 59, for "ethyl tetradecanoate read methyl tetradecanoate Signed and sealed this 5th day of April 1966',

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner of Patents 

1. A METHOD FOR CONVERTING FATTY ACID ESTERS INTO HIGHER ALKYL FATTY ACID ESTERS THAT COMPRISES REACTING AN ESTER SELECTED FROM THE GROUP CONSISTING OF METHYL AND ETHYL ESTERS OF FATTY ACIS HAVING BETWEEN ABOUT 8 AND ABOUT 30 CARBON ATOMS AND A TRIALKYL BORATE HAVING BETWEEN ABOUT 4 AND BOUT 18 CARBON ATOMS PER ALKYL GROUP, AT A TEMPERATURE OF BETWEEN ABOUT 185*C. AND ABOUT 300*C., UNDER A PRESSURE OF BETWEEN ABOUT 0.1 ATMOSPHERE AND ABOUT ONE ATMOSPHERE, AND CONTINUOUSLY REMOVING AN ESTER OF THE GROUP CONSISTING OF TRIMETHYL BORATE AND TRIETHYLBORATE. 